Any alliance that can produce a 126-seat majority in the 250-seat parliament can govern.

Tadic's coalition appeared assured of 103 seats while Nikolic's Radicals were poised to get 76.

If the Radicals joined forces with Kostunica's bloc and the Socialists, their combined strength would be 127 seats.

Andreja Mladenovic, Kostunica's spokesman, said he would hold talks in the coming days with other parties, including late president Slobodan Milosevic's Socialist party, whose support looked to be decisive for either camp.

Kosovo on agenda

The Socialists said they would start talks with Kostunica's party on Tuesday.

"At the moment, everyone is expecting Kostunica and the Radicals and us to form a coalition, but we still haven't talked," Branko Ruzic, a vice-president of the Socialists party, told Al Jazeera.

"We will also talk to Mr Tadic because he won the election.

"What will be the outcome, I'm not sure, but ... we need to have a government that keeps the national interests of Serbia.